[PATCH 0/7] dmaengine:omap-dma: Linked List transfer for slave_sg

Peter Ujfalusi
2016-07-14T12:42:35Z

Hi,

The following series with the final patch will add support for sDMA Linked List
transfer support.
Linked List is supported by sDMA in OMAP3630+ (OMAP4/5, dra7 family).
If the descriptor load feature is present we can create the descriptors for each
SG beforehand and let sDMA to walk them through.
This way the number of sDMA interrupts the kernel need to handle will drop
dramatically.

I have gathered some numbers to show the difference.

Booting up the board with filesystem on SD card for example:
# cat /proc/interrupts | grep dma
W/o LinkedList support:
27: 4436 0 WUGEN 13 Level omap-dma-engine

Same board/filesystem with this patch:
27: 1027 0 WUGEN 13 Level omap-dma-engine

Or copying files from SD card to eMCC:
# du -h /usr
2.1G /usr/
# find /usr/ -type f | wc -l
232001

# cp -r /usr/* /mnt/emmc/tmp/

W/o LinkedList we see ~761069 DMA interrupts.
With LinkedList support it is down to ~269314 DMA interrupts.

With the decreased DMA interrupt number the CPU load is dropping
significantly as well.

The series depends on the interleaved transfer support patch I have sent couple
of days ago:
https://lkml.org/lkml/2016/7/12/216

Regards,
Peter
---
Peter Ujfalusi (7):
dmaengine: omap-dma: Simplify omap_dma_start_sg parameter list
dmaengine: omap-dma: Complete the cookie first on transfer completion
dmaengine: omap-dma: Simplify omap_dma_callback
dmaengine: omap-dma: Dynamically allocate memory for lch_map
dmaengine: omap-dma: Add more debug information when freeing channel
dmaengine: omap-dma: Use pointer to omap_sg in slave_sg setup's loop
dmaengine: omap-dma: Support for LinkedList transfer of slave_sg

drivers/dma/omap-dma.c | 234 +++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 207 insertions(+), 27 deletions(-)

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2.9.1